This invention relates generally to power line communication systems and methods and components for use in, and aspects of, such systems and methods. One such aspect includes electronic genetics, the name given to the present invention's concept of uniquely identifying every device that can be connected to a power line installation both for energization and for information and control communication over the wires of the installation; with its unique identity, any such device can be connected to any power line installation to communicate with any other such device connected to that installation so long as the identity information is within the system of devices connected to the particular installation.
The wires of a power line installation which carry electricity to energize devices connected to the wires can also be used simultaneously to carry other electrical signals that convey information or control between devices connected to the wires. See, for example, U.S. Pat. No. 4,200,862 to Campbell et al.; U.S. Pat. No. 4,628,440 to Thompson; U.S. Pat. No. 4,638,299 to Campbell; and U.S. Pat. No. 5,491,463 to Sargeant et al. These patents refer to a power line communication protocol known as "X-10" and an extension of that protocol.
Under X-10 protocol as described in the aforementioned patents, a thirteen-bit code is transmitted from one device (e.g., a lamp) connected to a particular power line installation (e.g., in a home) to another device (e.g., a computer) also connected to the same installation. In one disclosed technique, each bit after four predetermined start bits is transmitted in true and complement form at the zero crossings of consecutive half cycles of an alternating current power signal also carried on the wires of the power line installation. These bits are transmitted using an alternating current signal having a frequency much higher than the frequency of the power signal. Using this technique the first device can advise the second device that it is on or off, for example. As another example, the first device can send a code to control the second device to turn on or turn off.
Although the X-10 protocol has advantages, such as in its encoding and transmission techniques, a significant shortcoming is its inability to accommodate either large numbers of devices connected to a power line installation or sophisticated information or control transactions. Even the extended code version described in the aforementioned Sargeant et al. patent is limited. Furthermore, devices are identified only within the context of the particular system in which they are connected; the devices do not have unique identities that are universal in scope (i.e., that they are always identified by no matter to what particular power line installation they are connected). As a result, these previously disclosed power line communication techniques have not been widely adopted for use in commercial or industrial installations or where complex information and control are needed.